Synthesis And Its Absorption Properties Of Polysaccharide-based Hydrogels

Hydrogels are cross-linked networks of hydrophilic polymer that are capable of retaining water without dis integration. These hydrogels have exhibited potential for app lic ation in many field. In this thes is, a kind of polysaccharide based hydrogels with excellent water absorbency properties were synthes ized by graft copolymerization of acrylic ac id and acrylic amide through modified the traditional preparing process. The factors that influence the liquid absorbency were studied as well.The optimal conditions of chitosan-based hydrogels were as follolws: temperature was 40℃, CTS dosage was 5.0 wt%, AAm amount was 25 wt%, the weight of crosslinker and initiator was 0.1 wt% and 1.0 wt%, respectively, m(AA):m(CTS) =10:1 and the neutralization degree was 60%. The maximum absorbency of distilled water, 0.15 mol/L NaCl and CaCl2 were 616 g/g, 58 g/g and 11 g/g, respectively. While the optimal conditions of hemic ellulose based hydrogels were as follows: temperature was 40℃, hemicellulose dosage was 5.0 wt%, AAm amount was 25 wt%, the weight of crosslinker and initiator was 0.1 wt% and 1.0 wt%, respectively, m(AA):m(HC) =10:1 and the neutralization degree was 70%. The maximum absorbency of distilled water, 0.15mol/L NaCl and CaCl2 were 603 g/g, 46 g/g and 9 g/g, respectively.Based on the optimal condition of chitosan based hydrogels mentioned above, a kind of rapid adsorption of chitosan-based hydrogels were synthes ized as well. The optimal conditions were as follows : temperature was CTS amount was 5.0 wt%, AAm dosage was 25 wt%, the weight of crosslinker and initiator was 0.1 wt% and 1.0 wt%, respectively, m( AA) :m(CTS)=10:1, the neutralization degree was 60%, m(Na HCO3) was 300 mg, reaction temperature was 60℃, stirring time was 10 s and the curing time was 30 min. The water swelling degree of the rapid chitosan-based hydrogels reac hed 107 g/g. Then the characteristics of the hydrogels were investigated by the Schott swelling kinetics equation of second order fit and the initial swelling rate is calculated Kis and S∞. Results showed that sample SPH-8 has the largest Kis, its value reached 42.19(g/g)/min whic h indicated that the hydrogels has an excellent fast swelling properties.Moreover the adsorption properties of Pb2+ onto the polysaccharide-based hydrogels were investigated. Both the chitosan-based hydrogels and the hemicellulose-based hydrogels exhibited good adsorption properties. The equilibrium data was fitted to Langmuir and Freundlic h adsorption isotherms and was found that Langmuir model presented the best fit, showing maximum monolayer adsorption capac ity of 5.81 and 5.88 mg?g-1. Results indicated that the adsorption of Pb2+ onto the hyrogels was characterized by monolayer coverage.The prepared hydrogels were a kind of opaque, smooth, well-distributed and high res ilience hydrogels. After water absorbing, the sample became transparent without dis integration. SEM results showed that the swelling properties were mainly determined by the hydrogels microstructure, such as the pore density, uniform pore size and specific surface area. While the rapid adsorption of chitosan-based hydrogels reached swelling equilibrium quic kly. The hydrogels prepared in this thes is were a kind of novel materials with potential application prospect.